1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more specifically relates to a semiconductor device having an insulating substrate on which a semiconductor element is disposed connected to an external member and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, it is known that a semiconductor device has been used in versatile aspects such as power generation, power transmission and efficient utilization and/or reproduction of energy. As such semiconductor device, there is one configured to have an insulating substrate, on which a semiconductor element is disposed, connected to a cooling member. Further, in such semiconductor device, a case is disposed so as to accommodate therein the semiconductor element, and the interior of the case may be filled with resin.
In order to improve the productivity and reliability of such semiconductor device, for example, a direct-potting seal technique by which an epoxy seal resin with a filler dispersed therein is injected into the case is gaining popularity. However, in such semiconductor device, how to ensure a close contact between the insulating substrate and the cooling member is an issue.
For example, Japanese Patent Laying-Open No. 2000-200865 discloses a method performed in such a manner that an insulating substrate is preliminarily warped downward into a convex shape, the semiconductor elements are installed on the insulating substrate to form a module, and the module is secured by screws to the cooling member with a sort of heat radiation grease uniformly spread between the insulating substrate and the cooling member so as to ensure the close contact.
Moreover, Japanese Patent Laying-Open No. 8-236667 discloses a method performed in such a manner that an inner portion of the insulating substrate, where the semiconductor elements are installed, positioned inner to an outer edge thereof is pressed downward so as to warp into a convex shape, and the warped insulating substrate is pressed against the cooling member so as to improve the close contact between the insulating substrate and the cooling member.